This invention relates generally to automobile seat belt retracting systems and more specifically to the provision of an improved manually operable tension-relieving mechanism.
The invention is applicable to most common types of seat belt and retracting spool systems. It has been found in those systems including a seat belt retractor that a retractor force for windably retracting the belt about a spool applies a constant pressure upon the vehicle occupant and may result in discomfort or displeasure. It is thus desirable to have means which maintain the belt at other than a fully tensioned position against the occupant's body by maintaining the belt at a slightly protracted or slackened position granting the occupant a small degree of freedom of movement without the belt imparting force to the occupant but maintaining the belt in a proper position for providing emergency restraint.
It is further desirable to provide a system for relieving tension that may be selectively manually engaged by the occupant with relative ease and that otherwise is disengaged so as not to impart drag to rotation of the retractor spool.
It is intended that this invention be particularly applicable to otherwise passive retraction devices that lock-up in emergency conditions. These devices typically have an internal ratchet in communication with the retracting spool that is engaged by a pawl that prevents protractive rotation of the spool during emergency conditions. This pawl and spool arrangement may be of two types, the first known as "web sensitive" wherein the pawl and spool assume the lock-up condition upon a sudden protraction of the seat belt as when the occupant is suddenly thrown forward. The second type is known as "vehicle sensitive" and typically incorporates an inertia mass that acts as a pendulum to cause lock up whenever the vehicle experiences excessive acceleration or deceleration.